The long-term objective of this research is to further our understanding of brainstem cellular, molecular, and network mechanisms of REM sleep regulation. Specifically, the goal of this renewal application is to investigate the molecular mechanisms within the cholinergic cell compartment of the pedunculopontine tegmentum (CCC-PPT) and dorsal subcoeruleus nucleus (SubCD) with respect to their roles in homeostatic regulation of REM sleep. The central hypothesis of this proposal is that homeostatic regulation of REM sleep and phasic pontine- wave (P-wave) activity are actively regulated by the interaction between brain-derived neurotrophic factor (BDNF) receptors (tropomyosin-related kinase B [TrkB]) and extracellular signal-regulated kinase1/2 (ERK1/2) signaling in the CCC-PPT and SubCD. Three specific aims have been designed to systematically test this hypothesis: 1. Test the hypothesis that during selective REM sleep deprivation, increased slow-wave sleep and increased expression of BDNF in the CCC-PPT are critical for the development of homeostatic drive for REM sleep, and under the same conditions, increased BDNF expression in the SubCD is critical for the homeostatic regulation of P-wave activity. This goal will be achieved by measuring homeostatic drive-associated changes in BDNF levels in the CCC-PPT, SubCD, and in a number of control areas at different intensities of increased REM sleep homeostatic drive. 2. Test the hypothesis that the interaction between BDNF TrkB receptors and ERK1/2 signaling in the CCC-PPT is critical for the homeostatic regulation of REM sleep, and that this same interaction in the SubCD is critical for the homeostatic regulation of P-wave activity. To test this hypothesis, at the beginning of a selective REM sleep deprivation period we will apply a BDNF TrkB receptor inhibitor, ERK1/2 activation inhibitor, or vehicle control into either the CCC-PPT or SubCD of rats, in order to block the increased homeostatic drive for REM sleep. 3. Test the hypothesis that, in heterozygous BDNF knockout (BDNF+/-) rats, decreased BDNF production in the CCC-PPT attenuates homeostatic regulation of REM sleep, and decreased BDNF production in the SubCD attenuates homeostatic regulation of P-wave activity. To test this hypothesis, at the beginning of the selective REM sleep deprivation period we will apply BDNF either into the CCC-PPT or SubCD of BDNF+/- rats. All of these experiments will be performed on adult, freely moving rats. We believe that the results of these studies will extend the leading edge of knowledge on the basic neurobiological mechanisms of REM sleep regulation. Also, for the first time, these results will launch a new area of investigation aimed at understanding the localized cellular and molecular mechanisms of homeostatic regulation of individual physiological signs of REM sleep. We believe that the results of these studies will shed light on the neuro-pathological mechanisms of REM sleep homeostatic regulatory dysfunctions in a number of psychiatric and neurological disorders (e.g., endogenous depression, schizophrenia, Alzheimer's, Huntington's, Parkinson's, and stroke), and will help us to design therapeutic interventions to eliminate these dysfunctions.